Osmose aktiengesellschaft



UNITED smgnggngnnr carton.

BOTHO SCHWERILLOF FRANKFORT-ON-THE-MAIN, GERMANY, ASSIGNOR TO ELEKTRO- OSMOSE AKTIENGESELLSCHAFT, (GRAYF SCHWERIN GESELLSCI-IAFT,) 0F FRANK- FOR-T-ON-THE-MAIN, GERMANY, A CORPORATION.

METHOD FOR MODIFYING THE ELECTRIQAL CHARGE OF DIAPHRAGMS.

Specification of Letters Patent.

Patented Dec. 23, rain.

No Drawing. Application filed November 16, 1914, Serial No. 872,4 43. Renewed October 17, 1919. Serial i No. 331,505.

To all whom it may concern:

Be it known that I, BOTI-IO SoHwnaIN, a subject of the German Emperor, residing at Frankfort-on-the-Main, Germany, have invented certain new and useful Improvements in Methods for Moditylng the Electrical Charge of Diaphragms, of whloh the following is a specification.

In the separation of collo1d mixtures, the purification of colloids, and other processes based on electro-osmotic principles 1n which diaphragms are employed, it has been proved that the electrical nature of the diaphragm, and its charge, are very lmportant; for instance, as shown by the lnventor, the fractionation of a given colloid from a liquid can be brought about by the choice of a suitably charged diaphragm. By e1nploying a diaphragm conslstmg of various substances mixed together, such as coru ndum and carborundum, the desired potential can be attained.

It has been proved that the electrlcal character of a diaphragm can be changed arbitrarily between wide limlts by altering its degree of adsorption. This can be achieved either by causing the diaphragm material to adsorb a suitable substance, or by the partial or complete removal of such substance already present in the material, either by electro-osmotic or other means.

In this way diaphragms are obtained, which are suitable for the most complicated processes of separation.

As examples may be given: The increase of the positive charge of a leather diap'hragm by adsorption of chromic oxld. In the same way organic coloring matters of a positive or negative nature allow extremely wide variations, whether plant, animal, or inorganic diaphragms are employed.

As an example of the change in a charge of a diaphragm through adsorption, the following example can be mentioned.

A diaphragm made of viscose has a negative charge. If however, the viscose is colored, it is possible to change the charge of the diaphragm, if a positive coloring matter is used, as this is adsorbed by the V15- cose and determines the degree of the change in the charge. If, for instance the viscose is colored with methylene blue, which possesses a positive charge, then the viscose diaphragm becomes charged positively. If a gelatin solution is treated by osmosis be,- tween diaphragms in which the cathode diaphragm consists of viscose, then certain of the positive colloidal parts of the gelatin come into the cathode chamber. If to the solution, aluminum oxid is added, there follows an adsorption of the same on the negative diaphragm, which is changed thereby so as to be more positively charged. In this manner, the movement of certain electropositive substances is delayed in the cathode chamber. As above mentioned, the charge of a diaphragm can be changed not only through adsorption but also through the leaching out of a body originally combined with the diaphragm. If for instance, a weak negative clay diaphragm is cooked with caustic soda, then some of the silicic acid in the clay is leached out and it overbalances the effect of the aluminum oxid on the charge of the clay diaphragm. This becomes more or less indifferent in character.

Since the electrical charge of a diaphragm can be varied by adsorption, it is possible to maintain, during a continuous working process, that charge which is most favorable to the development of the process.

Thus under suitable conditions the electroosnlotic process can be so directed that the adsorbed substances, whether originally present or previously brought on to the diaphragm, can be partially or totally removed during the course of the process. We have thus to do with a diaphragm having a variable charge, and it is even possible under certain circumstances during one and the same workin process to change the charge of a diaphragm, for instance from a positive value to zero or even to a negative value. r

If in the example mentioned in the last place in the osmosis of gelatin the fluid becomes more acid, then the aluminum oxid previously adsorbed becomes dissolved again and there then takes place a migration of basic substances through the cathodic diaphragm which were previously held back. In this manner a change in the charge of the diaphragm, at the same time as a fractionation of the basis in the ordinary leather diaphragm by adsorption of chromic 10 Working of the process is obtained. 'oxid.

What I claim is: In testimony whereof I affix my signature 1. A method for modifying the electric in presence of two witnesses.

5 charge of a diaphragm by combining with I the diaphragm adsorptions of desired po- .BOTHO SGHWERIN' tential. Witnesses I 2. The method described herein, eonsist- JEAN GR ND,

ing in increasing the positive charge of a CARL GRUND. 

